A solid state laser, or laser diode, before it will emit electromagnetic radiation, must be cooled to cryogenic temperatures and excited by an outside source of energy. This source of energy emits radiation itself which the laser diode converts into a laser beam. Laser diodes generally are relatively inefficient, however, and thus convert into laser radiation only a small portion of the excitation energy, converting much of the remaining energy into heat. Because the efficiency of laser diode devices decreases with an increase in temperature, heat generated by the laser's inefficient use of its energy source exacerbates the inefficient operation of the laser. In order to counteract these heating and related operating problems, heat must be removed.
To remove heat and keep the laser cooled, laser systems tend to cool their laser diodes by connecting a closed-cycle helium refrigerator, by means of a cold finger, to the laser diode's mounting structure. The laser diode mount is placed adjacent to a cryogenically cold finger of a cryogenic refrigerator. The finger conducts the very low temperatures from the helium refrigerator to the laser device. A heater device is then connected to the laser mount to maintain it at a desired operating temperature corresponding to a desired radiation characteristic.
Cryogenic refrigerators create vibration during their operation, however, which if transmitted to the laser, detrimentally affects the performance of the lasing diode. These vibrations cause an instability in the diode output spectrum, and can cause modulation effects in the laser output. The cold finger may also cause large thermal gradients which can cause uneven laser diode cooling and can induce thermal stresses.
Various devices have been developed with the goal of achieving vibration isolation of a mechanical refrigerator from a cryogenically cooled laser diode. For example, thermal conductive straps as shown in U.S. Pat. No. 4,161,747, issued to Jennings, have been used. The basic limitation of the Jennings strap, however, is that it fails to impede all vibration transmission from the cold finger to the diode mount.
There is a definite need in the art for an improved vibration isolation mounting system. Accordingly, it is an object of the present invention to provide good vibration isolation between a mechanical cryogenic refrigerator and the laser diode mounting structure, while providing good thermal conductivity therebetween.